The idea behind doing textures in Photoshop is to add layer over layer of different textures and use Photoshop layer blending modes to mix and match these different layers. The layer blending modes I end up using most are: Multiply, Screen, Soft Light and Color Burn. Changing the contrast and brightness of the images that you use as your texture layers is also very important to get decent results, so don't forget that Curves and levels adjustments in Photoshop are your friends (Fig.08).

Fig.08

For the character, I hand-painted the texture in ZBrush using a method I learned from Scott Spencer in his book ZBrush Character Creation. The idea is to add layer upon layer of different color tones to get a skin-like polypaint. For areas where the bone is close to skin, use more yellow and white colors; for areas that do not have bones, such as ears and nostrils, use more red tints, and for areas where there are veins under the skin do a pass of blue and then red on top (Fig.09).

Fig.09

The best brush to use for this method is the Standard brush with one of ZBrush's default alphas (alpha 07) and Spray Stroke with Zintensity set to 0 and RGB intensity set to low values (5 - 20 more or less)(Fig.10).

Fig.10

After polypainting was done, a new texture was created from the polypaint and exported to Photoshop. I also exported the Normal map in a file, turned it to black and white in Photoshop, put it on top of the texture, blended it using Multiply blending mode, and knocked the opacity down. This makes the details such as wrinkles more emphasized. You could also mask by cavity in ZBrush and create another pass (Cavity map) to put on top of your texture. This gives you control over how strong your cavities will look in the final render. For the Specular map, all I did was turn the Normal map black and white and then, using a brush, painted different values of gray on a layer on top of it in Photoshop. The brighter the gray shade in the Specular map, the more shine you see in the corresponding areas in the render (Fig.11).